The Neutrino Hunters

Title: The Neutrino Hunters

Author: Ray Jayawardhana

Publisher: OneWorld, 2013 (First)

ISBN: 9781780743264

Pages: 243

Only a few years back, a storm of protests broke out in the Indian state of Kerala over the proposed construction of a neutrino observatory on the state’s border with Tamil Nadu. Politicians, including the then opposition leader of the state – who was uneducated – came on the scene amid much fanfare, extolling the dangers caused by neutrinos! Though the protests petered out in a few weeks, it was the first time ever in the world that neutrinos became controversial. It was projected out of all proportions by a section of the ignorant media who had no idea what they were talking about. ‘The Neutrino Hunters’ is a fine book that will alleviate all concerns a thinking person may normally have on what a neutrino is, and why it is incumbent on the scientific world to detect it. We are familiar with several byproducts of the research on nuclear physics that eventually made people’s lives better. Neutrino research is still in its infancy, but exciting possibilities abound for its further development. Ray Jayawardhana was born and raised in Sri Lanka. After receiving his PhD from Harvard, he is now Dean of the Faculty of Science at York University. He has bagged many awards and authored several books on popular science. His primary research areas include the formation and early evolution of stars, brown dwarfs and planets.

The atom’s nucleus is a storehouse of mysterious operations taking place spontaneously as if by magic. But don’t be mistaken – all the activities are catalogued in fine detail by the rules of quantum mechanics. Neutrons in the nucleus are generally stable, but they sometimes undergo a transformation to change into a proton, which is also a constituent of the nucleus. In this process, a proton is thus formed, in addition to an electron, which is a beta ray. This process is called beta decay. When this phenomenon was discovered in the early-20^th century, scientists found an anomaly, which was perplexing. If you tally the amounts of energies involved with the constituents which underwent change against the new particles which were formed, there was a minuscule shortage in the latter quantity. This is an apparent violation of the law of conservation of energy, which in physics is akin to blasphemy in a theocracy. Some scientists however, took the risk of claiming that beta decay doesn’t obey the sacrosanct rule of nature. Wolfgang Pauli, of the Exclusion Principle fame, suggested a way out of this dilemma. He postulated that the missing energy may be of the form of a new kind of particle, having no charge, but a very small mass. Since the term ‘neutron’ was already around to denote a different particle, this new particle was named ‘neutrino’, or ‘little neutron’ in the Italian language. The mass of the neutrino being very, very small, and having no charge, Pauli hazarded a guess that it may not be physically possible to detect a neutrino in the lab. Science is an avenue where challenges are met with gusto, by pioneers in search. Immediately after the identification of the particle, the academic community started the search for it.

The search party was successful in the mid-1950s when nuclear reactors became a craze for developed countries. Fred Reines and Clyde Cowan were triumphant in detecting neutrinos emerging from nuclear test explosions and ordinary nuclear reactors. It was evident for scholars that neutrinos being very light, it passes through the earth without colliding with another corpuscle. Massive detectors are required to trap such particles. An ingenious way was developed to address this issue. When neutrinos hit a particle of water or carbon tetrachloride or any such material, a neutron is converted into a proton, along with release of a photon. This photon produces visible light of a light blue shade. So, if large number of phototubes is arranged over a gigantic collection of such liquid, researchers may be able to detect the light flashes occurring rarely enough, even though trillions of neutrinos pass through the earth and each one of us every second. Scientists built massive detectors in mines, hundreds of meters down from the ground level, in order to avoid unwanted noise from neutrinos generated by atmospheric gases being hit by cosmic rays. Apart from this, the sun is the most abundant neutrino source on account of the nuclear reactions taking place in its core. John Bahcall made an estimate of the neutrinos produced normally in the sun which can be detected on earth. Another physicist, Ray Davis, set up a detector in Homestake gold mine in the U.S. Davis found only a third of the neutrinos predicted by Bahcall’s theory. A controversy raged on the soundness of the theory and the methods of detection. Later, researchers showed that neutrinos come in three varieties or flavours as they are called – electron neutrino, muon neutrino and tau neutrino – which oscillate between the states mid-flight on its journey to earth. As the detector was able to trap only one kind of neutrinos, the count appeared to be one-third of the total predicted by theory. This shows the commendable level of understanding we have reached on what happens in the sun’s core.

Neutrino bursts precede appearance of supernova events in the sky. Study of neutrinos is very relevant for understanding the processes going on inside stars during its origin, midlife, and end. In 1987, a supernova was seen suddenly on a cold February night in the Large Magellanic Cloud galaxy. Even though supernovae occur very frequently, one that can be seen by the naked eye is rare and was last observed way back in 1604. Naturally, astronomers were delighted to observe this phenomenon. It was also the time for neutrino hunters to jump in and take credit for their findings. Theory predicted that a neutrino stream generated in the supernova should have struck earth even before its visible light reached us. Don’t think that neutrinos travel faster than light – it is only that visible light may be obstructed by gas or dust clouds, but neutrinos pierce through them with ease. All the world’s leading neutrino detectors poured over their records and found that exactly such a stream had hit their instruments three hours before the celestial flare lit up the night sky.

Jayawardhana reserves the last chapter of the book to desperately enumerate the practical applications of neutrinos that are helpful to humanity. Even though we can wax eloquent at the dearth of funding insensitive politicians earmark for scientific research out of public funds, there is no denying that scientists have to show some benefits anticipated out of the new area of research for which money is being sought. Studying neutrinos is immensely helpful in learning more about the origin of the universe in its earliest seconds, the death throes of stars which spread the heavy elements essential for life in a supernova explosion and the processes going on inside the earth that maintains the temperature of its core. Moreover, as neutrinos are not hampered by any obstacles in its path, faster communication links can be developed out of an intense beam. The author’s arguments are earnest, but seem to be a little too farfetched, considering the still early stage of the neutrino theory.

The book is nicely written, with scientific ideas conveyed in an accessible manner to all classes of readers. Jayawadhana’s description of the ‘IceCube’ detector in Antarctica provides an exciting introduction to the narrative that follows. Also, his firsthand experience in visiting the Sudbury Neutrino Observatory (SNO) in Canada, by going more than a mile underground in a mine elevator is a fine example of the author’s power to rivet the attention of the reader. The book includes extensive Notes for follow up reading and a helpful Index. A neat timeline of major events associated with neutrinos and an impressive glossary adds much utility to the book. A few monochrome photographs are also included, but lack correlation with the text. The book follows the standard pattern of including short biographical sketches of scientists mentioned in the text. If you are already familiar with them from other books, this may appear a bit dull.

The book is highly recommended.

Rating: 4 Star